WPRINTF(3)                                          Linux Programmer's Manual                                         WPRINTF(3)



NAME
       wprintf, fwprintf, swprintf, vwprintf, vfwprintf, vswprintf - formatted wide-character output conversion

SYNOPSIS
       #include <stdio.h>
       #include <wchar.h>

       int wprintf(const wchar_t *format, ...);
       int fwprintf(FILE *stream, const wchar_t *format, ...);
       int swprintf(wchar_t *wcs, size_t maxlen,
                    const wchar_t *format, ...);

       int vwprintf(const wchar_t *format, va_list args);
       int vfwprintf(FILE *stream, const wchar_t *format, va_list args);
       int vswprintf(wchar_t *wcs, size_t maxlen,
                     const wchar_t *format, va_list args);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       All functions shown above: _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE; or cc -std=c99

DESCRIPTION
       The  wprintf()  family  of  functions is the wide-character equivalent of the printf(3) family of functions.  It performs
       formatted output of wide characters.

       The wprintf() and vwprintf() functions perform wide-character output to stdout.  stdout must not be  byte  oriented;  see
       fwide(3) for more information.

       The  fwprintf() and vfwprintf() functions perform wide-character output to stream.  stream must not be byte oriented; see
       fwide(3) for more information.

       The swprintf() and vswprintf() functions perform wide-character output to an array of wide  characters.   The  programmer
       must ensure that there is room for at least maxlen wide characters at wcs.

       These functions are like the printf(3), vprintf(3), fprintf(3), vfprintf(3), sprintf(3), vsprintf(3) functions except for
       the following differences:

       o      The format string is a wide-character string.

       o      The output consists of wide characters, not bytes.

       o      swprintf() and vswprintf()  take  a  maxlen  argument,  sprintf(3)  and  vsprintf(3)  do  not.   (snprintf(3)  and
              vsnprintf(3) take a maxlen argument, but these functions do not return -1 upon buffer overflow on Linux.)

       The treatment of the conversion characters c and s is different:

       c      If no l modifier is present, the int argument is converted to a wide character by a call to the btowc(3) function,
              and the resulting wide character is written.  If an l modifier is present, the wint_t (wide character) argument is
              written.

       s      If  no  l modifier is present: The const char * argument is expected to be a pointer to an array of character type
              (pointer to a string) containing a multibyte character sequence beginning in the initial shift state.   Characters
              from the array are converted to wide characters (each by a call to the mbrtowc(3) function with a conversion state
              starting in the initial state before the first byte).  The resulting wide characters are written up  to  (but  not
              including)  the  terminating  null  wide character.  If a precision is specified, no more wide characters than the
              number specified are written.  Note that the precision determines the number of wide characters written,  not  the
              number  of bytes or screen positions.  The array must contain a terminating null byte, unless a precision is given
              and it is so small that the number of converted wide characters reaches it before the end of the array is reached.
              If  an l modifier is present: The const wchar_t * argument is expected to be a pointer to an array of wide charac-
              ters.  Wide characters from the array are written up to (but not including) a terminating null wide character.  If
              a  precision  is  specified,  no more than the number specified are written.  The array must contain a terminating
              null wide character, unless a precision is given and it is smaller than or equal to the number of wide  characters
              in the array.

RETURN VALUE
       The  functions return the number of wide characters written, excluding the terminating null wide character in case of the
       functions swprintf() and vswprintf().  They return -1 when an error occurs.

CONFORMING TO
       C99.

NOTES
       The behavior of wprintf() et al. depends on the LC_CTYPE category of the current locale.

       If the format string contains non-ASCII wide characters, the program will only work correctly if the LC_CTYPE category of
       the  current  locale  at  run  time  is the same as the LC_CTYPE category of the current locale at compile time.  This is
       because the wchar_t representation is platform- and locale-dependent.  (The glibc represents wide characters using  their
       Unicode (ISO-10646) code point, but other platforms don't do this.  Also, the use of C99 universal character names of the
       form \unnnn does not solve this problem.)  Therefore, in internationalized programs, the format string should consist  of
       ASCII  wide  characters only, or should be constructed at run time in an internationalized way (e.g., using gettext(3) or
       iconv(3), followed by mbstowcs(3)).

SEE ALSO
       fprintf(3), fputwc(3), fwide(3), printf(3), snprintf(3)

COLOPHON
       This page is part of release 3.25 of the Linux man-pages project.  A description of the project,  and  information  about
       reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



GNU                                                        2007-07-26                                                 WPRINTF(3)